Hox genes: changes to gene functions, changes to gene regulation

Question 1

what is a homeobox?

Answer 1

a DNA region, first found in homeotic genes, but also present in many other places

Question 2

homeodomain

Answer 2

60ish aa region coded by a homeobox- they act as a transcription factor for specific proteins

Question 3

tldr- what do hox genes do?

Answer 3

genes which specify where cells are along the head/tail of animals. they do this by encoding transcription factors which then encourage tissues to ‘act’ like what they are supposed to be

Question 4

spatial colinearity

Answer 4

hox genes are expressed in the same order along the body as they are along the chromosome

Question 5

examples of ‘cluster breaking’

Answer 5

seems to break up twice in the drosophila lineage, happens fairly often- relaxed selection pressure in a lot of cases

Question 6

temporal colinearity

Answer 6

a feature of vertebrate hox genes- repression along a cluster can be gradually removed over a few days, through spreading histone modifications

may be a reason for spatial colinearity- but it’s not universal so?

Question 7

hox gene duplications

Answer 7

a lot of fish have 8 clusters (duplication), salmon have 16

Question 8

example of hox genes which have changed function

Answer 8

Ftz- segmentation gene now, not spatial location
Bcd- now involved in early patterning

Question 9

ex-hox gene now important in lepidoptera

Answer 9

Zen cluster (look up significance of this at some point lol i dont remember)

Question 10

how can a hox gene stop being a hox gene?

Answer 10

gene expression moving, leading to functional redundancy, where a new gene can then take its place??

Question 11

example of a hox mutant changing something other than body plan

Answer 11

Hoxb13 mice- changes tail length, probably not a hox gene as we know it now- also more distant from the rest of the hox cluster- escape?

^^ see this in sheep also